The present invention relates to a method of determining cutting forces, and also to a calculator which utilizes the new method.
Turning and boring operations become productive when machining conditions such as cutting speed, feed per revolution, and depth of cut are properly selected according to the cutting tool material and geometry, mechanical properties of the workpiece material, and technical characteristics of the machine tool. Besides that, ability to determine cutting forces allows for setting maximum productivity within machine tool power capacity and prevents stalling the machine tool. The cutting forces are: tangential, feed, and radial. Tangential force Ft is determined by the formula, which is used when turning and boring as disclosed in E. Isakov xe2x80x9cReassessing power factorsxe2x80x9d, American Machinists, December 1996, pages 43-45.
Ft=396000dfp (lbf)
where d=depth of cut, in., f=feed rate, in/rev.
p=specific power, hp/in.3/min, and 396000 is a conversion factor.
Determined tangential force Ft and selected cutting speed Vc allow for determination of the required machining power P:
P=FtVc/33000(hp)
where 33000 is a conversion factor.
Feed Ff and radial Fr forces are proportional to tangential force Ft. It is a common practice to consider that Ff=0.5 Ff and Fr=0.25 Ft. Unfortunately, this method of feed and radial force determination has acceptable accuracy only when applied to some carbon steels in annealed and normalized conditions.
Another known method as disclosed in E. Isakov xe2x80x9cReassessing power factorsxe2x80x9d, American Machinists, December 1996, pages 43-45 provides more accurate formulas for determination of feed Ff and radial Fr forces at the following cutting conditions.
Ff=0.581 Ftxe2x88x9218.3: AISI 1018 and 316 steels, 140-200 HB, 0.008-0.01 ipr feed, 0.06-0.3 in. depth of cut
Ff=0.458 Ftxe2x88x926.6: AISI 1045 and 4140 steels, 140-200 HB, 0.012-0.02 ipr feed, 0.06-0.3 in. depth of cut Ff=0.556 Ftxe2x88x925.3: AISI 4340 and H11 steels, 205-260 HB, 0.008-0.012 ipr feed, 0.06-0.3 in. depth of cut Ff=0.477 Ft+7.3: AISI 4140 and 410 steels, 205-260 HB, 0.015-0.02 ipr feed, 0.06-0.3 in. depth of cut
Fr=0.145 Ft+32.0: AISI 1018 and 316 steels, 140-200 HB, 0.01-0.02 ipr feed, 0.06-0.15 in. depth of cut
Fr=0.182 Ftxe2x88x929.3: AISI 1045 and 4140 steels, 140-200 HB, 0.01-0.02 ipr feed, 0.18-0.3 in. depth of cut
Fr=0.111 Ft+40.7: AISI 4340 and H11 steels, 205-260 HB, 0.008-0.012 ipr feed, 0.06-0.3 in. depth of cut
Fr=0.143 Ft+48.7: AISI 4140 and 410 steels, 205-260 HB, 0.015-0.02 ipr feed, 0.06-0.3 in. depth of cut.
These formulas are utilized in the electronic xe2x80x9cMetalcutting Force and Power Calculator: Turning and Boringxe2x80x9d E. Isakov xe2x80x9cMetalcutting Force and Power Calculatorxe2x80x9d (Turning, Boring, Milling)xe2x80x9d on the 3.5 inch diskette.kennametal, Inc. 1998.
Limitations of these formulas are as follows:
Applied only to a few grades of carbon (1018 and 1045), alloy (4140 and 4340), stainless (316 and 410), and tool (H11) steels having Brinell hardness numbers from 140 to 260 HB.
If hardness of the above-mentioned work materials is indicated in other then Brinell hardness numbers, the equivalent hardness numbers should be found in the appropriate handbooks.
Applied to the feed rates from 0.008 in./rev. to 0.020 in./rev.
Applied to the depth of cuts from 0.060 in. to 0.300 in.
Accordingly, it is an object of the present invention to provide a method of determining cutting forces, and a calculator which uses the method, which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides in a method of determining cutting forces in accordance with which the work materials are divided into special new groups which differ from one another by Brinell hardness, and feed and radial forces are determined from a tangential force differently for the material of each group and also differently for a turning process and for a boring process.
In accordance with another feature of the present invention a calculator is provided in which the determination of feed and radial forces is performed in accordance with the above specified inventive method.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments.